The present invention relates to a lighting device for a vehicle, and, more particularly, to a lighting device comprising a light source and a reflector which has a reflecting surface with a basic shape which is designed so that light generated by the light source is reflected from it as a light beam and which has an undulating or wave-like structure with alternating successive scattering wave sections and concentrating wave sections superimposed on its basic shape, by which the light beam reflected by the reflecting surface is made uniform.
This type of lighting device is described in European Patent Document EP 0 581 661 A. This lighting device has a light source and a reflector. The reflector has a reflecting surface whose basic shape is formed or designed so that light issuing from the light source is reflected as a light beam with predetermined characteristics. In order to make the intensity distribution produced by the light beam uniform, which means to avoid regions with undesirably strong or weak illumination, a wave structure with successive scattering and concentrating wave sections is superimposed on the reflecting surface of the reflector. This wave structure should be determined by random variations in the basic form of the reflecting surface. In this reference nothing is stated regarding the size of the scattering and concentrating wave sections, although this is of essential significance for the desired uniformity of the light beam and in which regions with undesirably high light intensity can be provided through the concentrating wave sections. A sufficiently uniform reflected light beam cannot be attained under the circumstances with the known lighting device. Wave sections are superposed on the reflecting surface in horizontal longitudinal cross-section and also in vertical longitudinal cross-section. A deflection of the light beam in both the horizontal and vertical directions is thereby caused relative to the light beam that would be reflected by a surface with only the smooth basic shape of the reflecting surface, so that particularly with dimmed headlights, such as low-beam headlights or fog lights, a deflection of the light beam in a vertical direction over the light-dark boundary is not desired and/or permitted. The known lighting device of the above-described type is thus not suitable for use as a dimmed or low-beam headlight.
It is an object of the invention to provide a lighting device for a vehicle of the above-described type which does not have the above-described disadvantages.
This object, and others which will be made more apparent hereinafter, is attained in a lighting device comprising a light source and a reflector which has a reflecting surface with a basic shape which is designed so that light generated by the light source is reflected from it as a light beam and which has an undulating or wave-like structure with alternating successive scattering wave sections and concentrating wave sections superimposed on its basic shape, by which the light beam reflected by the reflecting surface is made uniform.
According to the invention the extent of the scattering wave sections perpendicular to their surface lines is substantially larger than the extent of the concentrating wave sections perpendicular to their surface lines.
The lighting device according the invention has the advantage that regions with undesirably greater illumination intensity can be avoided by the stated larger extent of the scattering wave sections relative to the concentrating wave sections so that a sufficiently uniform reflected light beam can be obtained.
Advantageous embodiments and features of the invention are claimed and described in the appended dependent claims. For example in a preferred embodiment of the lighting device the scattering wave sections and the concentrating wave sections are arranged so that the surface lines are at least approximately vertical. Furthermore advantageously the light beam reflected by the reflecting surface has an upper light-dark boundary including an approximately horizontal section and a climbing section climbing upward from the horizontal section, and the wave sections are arranged in a part of the reflecting surface which produces the climbing section of the light-dark boundary, so that the surfaces lines extend at least approximately perpendicular to the climbing portion and the wave sections are arranged in a remaining part of the reflection surface so that the surface lines of the wave sections extend at least approximately vertical.
In another preferred embodiment the ratio of the extent of the scattering wave sections perpendicular to the surface lines of the scattering wave sections to the extent of the concentrating wave sections perpendicular to the surface lines is about 5:1 to 50:1.
In various other embodiments of the invention the light beam reflected from the reflecting surface is divergent or convergent and the scattering wave sections and the concentrating wave sections are respectively convex and concave, or concave and convex.